Reproductive cycle of the velvet swimming crab Necora puber (L.) (Decapoda, Brachyura, Portunidae) on the east coast of Ireland

Abstract

An unfished population of Necora puber, in a coastal area just south of Dublin, was sampled monthly between August 1986 and November 1987 using baited creels. The reproductive cycle was analysed using gonad stages, the incidence and size distribution of ovigerous females and developmental stages of the egg masses. Both sexes started to breed at a carapace width of about 50 mm when they were about one year old. Seven ovarian and six testicular stages were recognised, both macro- and microscopically. The ovary underwent continuous cyclical changes and there was no distinct winter resting period. All ovigerous females had developing or ripe ovaries and they may thus produce more than one brood in a season. The main breeding season started in February with the greatest number of ovigerous females found in March-June and a peak in May. Less than 10% of females were ovigerous from August to January. The main periods of larval release were April, June and August. Spawning and recovering males were present throughout the year. Differences between the observed reproductive cycle and those studied in Britain and Spain are discussed.